Primary carpet backing and tufted carpet comprising the same

ABSTRACT

A primary carpet backing having at least a nonwoven layer of fibers, the nonwoven layer of fibers including fibers having a higher melting component and a lower melting component, wherein the fibers are 12 to 20 vol. % of the lower melting component. After tufting, a tufted carpet backing having the primary carpet backing exhibits improved stitch holding performance.

BACKGROUND

The disclosure pertains to primary carpet backings comprising a nonwoven layer of fibers. The disclosure also pertains to tufted carpets comprising such primary carpet backings.

Primary carpet backings for tufted carpets comprising a nonwoven layer of fibers have been known for many years. The nonwoven primary backings used in tufted carpet production are generally either nonwovens comprising a backbone of polyester, for example polyethylene terephthalate (PET) fibers, or nonwovens comprising a backbone of polypropylene fibers. The term “fibers” as used herein refers both to staple fibers and filaments.

In general, the polypropylene or polyester fibers are filaments in the range of 1 to 25 dtex, preferably in the range of 2 to 20 dtex, most preferably in the range of 5 to 15 dtex providing acceptable processing stability. The unit dtex defines the fineness of the filaments as their weight in grams per 10,000 meters.

The backbone fibers of the nonwoven primary backing can be entangled by mechanical needling and/or hydroentanglement with fine water jets and optionally bonded with a chemical binder.

Alternatively, the backbone fibers of the nonwoven primary backings can be thermally bonded, for example by calendaring or through-air bonding or the like, using a lower melting polymer, i.e., which melts at a lower temperature, which is present in the form of fibers or which has been added to the nonwoven layer of fibers as a powder or as granulate. When the lower melting polymer is present in the form of fibers, the lower melting polymer can be present as separate monocomponent fibers, or the lower melting polymer can be present together with the backbone polymer in the same fibers in so-called bicomponent or in multicomponent fibers. Bicomponent fibers are well known in the art, for example as side-by-side, core/sheath or segmented pie fibers. Alternatively, fibers composed of a single polymer, but with varying crystallinity along the length of the fiber, can be used as bicomponent fibers as varying crystallinity results in fiber sections consisting of polymer with different melting points along the length of the fiber.

The process of making a tufted carpet comprises the steps of providing a primary carpet backing material into a tufting machine, tufting the primary backing material with tufting yarns to obtain a greige carpet with a face side showing tufts and a back side where back stitches are formed. A tuft is the visible part of the tufting yarn on the face side of a greige or carpet. A back stitch is the visible part of the tuft yarn on the backside of a greige carpet.

Over the years, nonwoven primary carpet backings have been improved constantly in order to meet the ever more stringent demands of carpet manufacturers and consumers. New tufting techniques such as high-low tufting to produce carpets with high tufts and low tufts in a single carpet require primary backings with improved stitch holding capabilities to hold the tufts in place in the tufting process. Of particular importance are improving the appearance of the finished carpet, facilitating tuftability, i.e. by providing lower tuft-needle penetration resistance and reduced needle deflection during tufting, avoiding backtags, increasing stitch holding performance and reducing noise during tufting.

The newly formed tufts in the greige carpet are held into place by the stitch holding capacity of the primary backing material. Stitch holding is the force required to remove a loop from a greige carpet from the back side. The stitch holding determines how strong the interaction is between the primary carpet backing and the tufting yarn in the greige carpet. The stitch holding determines the chance on failures in the subsequent processing steps after tufting until the tufts are locked into place, for example in the application of a pre-coat. These processing steps can for example comprise dyeing, pre-coating, tentering, steaming and/or winding of the greige carpet and/or transport of rolls of greige carpet. Each of these processing steps of the greige carpet are executed under severe conditions regarding temperature and/or applied tensions, which pose high demands to the primary carpet backing material.

The tuft-bind performance of the pre-coat determines mainly how well the tufts are held in place in the pre-coated carpet. After pre-coating, a heavy layer may be coated onto the back side of the pre-coated carpet and/or a secondary carpet backing can be applied to obtain a finished tufted carpet.

The primary carpet backing should exhibit good tuft holding capabilities. The primary carpet backing should have a high stitch holding capacity to hold the tufts in place during the dynamic process of tufting in order to obtain tufts of essentially the same height for an even carpet surface in the greige carpet. The stitch holding capacity of a primary carpet backing is the ability to put the tufts in place during the tufting process where the tufts are formed and to hold the tufts in place, directly after being formed, during the formation of the following tufts during the tufting process. It determines the face appearance and the backtags of the greige carpet during the tufting process. A backtag is a loose or uneven backstitch in a greige carpet, in essence, a tuft which was formerly on the carpet face that is now (partially) on the back side. During subsequent processing steps, like dyeing and precoating, the stitch holding of the primary backing should be high enough to retain the carpet surface as produced during tufting.

To lock the tufts in the greige carpet into place, a pre-coating can be applied to the back side of the greige carpet. The tuft bind is the force required to remove one tuft completely out of the (pre-coated or finished) carpet from the face side. It determines how strong the adhesive bond is between the pile fibers and the adhesive coating applied to the greige carpet. The pre-coat is generally applied either as a latex solution or as a foamed latex to the back side of the greige carpet and subsequently, the latex is dried to form bonds between the base of the tufts and the primary carpet backing.

BRIEF SUMMARY

It is an object of the embodiments to provide primary carpet backings having improved stitch holding capacity.

The object of the embodiments is achieved by a primary carpet backing comprising a nonwoven layer of fibers, wherein the nonwoven layer of fibers comprises fibers comprising a higher melting component and a lower melting component characterized in that the fibers consist for 12 to 20 vol. % of the lower melting component.

DETAILED DESCRIPTION

The term “fibers” as used herein refers both to staple fibers and filaments. Preferably, the fibers have a linear density in the range of 1 to 25 dtex, preferably in the range of 2 to 20 dtex, most preferably in the range of 5 to 15 dtex to provide sufficient processing stability. Preferably, the fibers are filaments to further improve the processing stability of the primary carpet backing.

At least 50% of the fibers of the nonwoven layer of fibers of the primary carpet backing may consist for 12 to 20 vol. % of the lower melting component. Preferably at least 75%, more preferably at least 85%, even more preferably at least 95%, most preferably all of the fibers of the nonwoven layer of fibers of the primary carpet backing consist for 12 to 20 vol. %, of the lower melting component.

The fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for 12 to 20 vol. % of the lower melting component. Preferably, the fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for 14 to 18 vol. %, more preferably 15 to 17 vol. %, most preferably 16 vol. %, of the lower melting component. Such a primary carpet backing exhibits improved stitch holding capacity and/or yields after tufting a tufted carpet backing exhibiting an increased stitch holding.

When the fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for less than 12 vol. % of the lower melting component, bonding of individual filaments in a thermally bonded primary backing will not be sufficient. The primary carpet backing comprising fibers consisting for at least 12 vol. % of the lower melting component has no, or only a low risk of, loose fibers extending from the primary carpet backing, which are prone to cause problems during the tufting process. For example, loose fibers may get wound onto rotating rollers during unwinding of the primary backing and/or during entry into the tufting machine, or the loose fibers may become entangled in the tufting needles during the tufting process, which can cause interruption of the tufting process and reduction in productivity.

Preferably, the nonwoven layer of fibers has a uniform composition to achieve consistent stitch holding capacity and stitch holding performance throughout the primary carpet backing and throughout the tufted carpet. Uniform composition as used herein has to be understood that the type and amount of fibers throughout the nonwoven layer is constant within the limits encountered in standard nonwoven processes.

The fibers of the nonwoven layer of fibers of the primary carpet backing may be bicomponent fibers or multicomponent fibers. Multicomponent fibers may for example be in the form of segmented pie fibers, of core/intermediate sheath/outer sheath construction, or side-by-side-by-side configuration. The fibers may be hollow bicomponent or hollow multicomponent fibers to reduce the performance to weight ratio.

Preferably, the fibers of the nonwoven layer of fibers of the primary carpet backing are bicomponent fibers. The bicomponent fibers may be any type of bicomponent fibers, such as for example side-by-side, core-sheath, segmented pie and/or islands-in-the-sea fibers. More preferably, the bicomponent fibers are core/sheath bicomponent fibers. Preferably, the sheath of the core/sheath bicomponent fibers comprises the lower melting component. For islands-in-the-sea fibers, the sea preferably comprises the lower melting component.

The higher melting component may be any thermoplastic polymer. However, the higher melting component preferably comprises a polyester such as for example poly(trimethylene terephthalate) (PTT), polyethylene naphthalate (PEN) and/or polyethylene terephthalate (PET), a co-polyester, a polyamide such as for example polyamide-6,6 (PA6,6) and/or polyamide-6 (PA6), a co-polyamide, a polyolefin such as for example polypropylene and/or a mixture thereof.

The lower melting component may be any thermoplastic polymer having a lower melting temperature than the higher melting component. The lower melting component has a melting temperature at least 5° C. lower than the melting temperature of the higher melting component. Preferably, the lower melting component has a melting temperature at least 10° C. lower, more preferably at least 20° C. lower, even more preferably at least 30° C. lower, most preferably at least 50° C. lower than the melting temperature of the higher melting component.

However, the lower melting component preferably comprises a co-polyester, such as, for example, polybutylene terephthalate (PBT), a polyamide such as for example polyamide-6 (PA6), a co-polyamide, a polyolefin such as for example polypropylene, or a mixture thereof.

In a preferred embodiment, the higher melting component of the bicomponent fibers comprises a polyester, more preferably polyethylene terephthalate (PET), and the lower melting component comprises a polyolefin, more preferably polypropylene. The PET/Polyolefin fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for 12 to 20 vol. % of the lower melting component. Preferably, the fibers consist for 16 to 20 vol. %, more preferably 18 to 20 vol. %, most preferably 20 vol. %, of the lower melting component to obtain low stich holding capacity values, smooth backstitches and/or improved mendability.

In another preferred embodiment, the higher melting component of the bicomponent fibers comprises a polyester, more preferably polyethylene terephthalate (PET), and the lower melting component comprises a polyamide, more preferably polyamide-6 (PA6). The PET/PA fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for 12 to 20 vol. % of the lower melting component. Preferably, the fibers comprised in the nonwoven layer of fibers of the primary carpet backing consist for 14 to 18 vol. %, more preferably 15 to 17 vol. %, most preferably 16 vol. %, of the lower melting component to obtain low stich holding capacity values, smooth backstitches and/or improved mendability.

The primary carpet backing is preferably thermally bonded by means of the lower melting component of the bicomponent fibers. Thermal bonding may be achieved by any known thermal bonding process, such as, for example, calendaring and/or through-air bonding.

The strength and strain at break of the greige carpet is important, especially when the tufted carpet is to be used as automotive carpet. On the basis of the geometry of the car body floor the carpet has to be bent, i.e., deformed, strongly in various areas. Especially pronounced of course is the deformation in the area of the transmission tunnel of a car. In order to accommodate the locally high deformations, the strength at break and elongation at break of the tufted carpet must be sufficient.

The primary carpet backing may comprise one or more additional layers of fibers. Each additional layer of fibers can be selected from a nonwoven layer of fibers, a woven layer of fibers or a scrim. For example, a scrim may be incorporated into the primary carpet backing to further improve the dimensional stability of a carpet tile. A woven layer of fibers may be incorporated into the primary carpet backing for example to supply additional strength in the warp and weft direction of the woven layer. A further nonwoven layer of fibers comprising a different polymer or different polymers may be incorporated into the primary carpet backing, for example, to adjust the dyeability of the face side of the primary backing and/or to prevent latex bleeding.

A film may be incorporated into the primary carpet backing, for example, to provide a barrier against latex bleeding. Latex bleeding is to be understood to mean that a pre-coat applied to back side of the greige carpet, i.e., the tufted primary carpet backing, migrates through the primary backing to become visible at the face side of the tufted carpet.

The fibers of each of the additional layers of fibers may comprise at least two different polymers. The at least two different polymers may be present in bicomponent fibers or may exist in separate fibers in the nonwoven layer of fibers. Alternatively, the fibers of each of the additional layer of fibers may consist of a single polymer.

Preferably, the nonwoven layer of fibers in the primary backing according to the embodiments has a uniform composition to achieve consistent delamination strength with additional layers incorporated into the primary backing.

In an embodiment, a tufted carpet comprises the primary carpet backing described above.

EXAMPLES

All samples were spunbonded using commonly known technology for depositing layers of filaments on top of each other on a collector surface. After deposition, the deposited layers of filaments were thermally bonded to form a single coherent nonwoven layer of fibers.

Example 1

The primary backing of example 1 was produced by depositing four layers of filaments on a collector surface, each layer of filaments having a weight of 27.5 g/m². The basic weight of the primary backing of example 1 amounted to 110 g/m². The filaments were all of the core/sheath type in a core/sheath ratio of 84/16 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component. The linear density of the filaments was 15 dtex.

The primary backing of comparative example 1 consisted of four layers of filaments, each layer of filaments having a basic weight of 27.5 g/m². The basic weight of the primary backing of example 2 amounted to 110 g/m². The filaments were all of the core/sheath type in a core/sheath ratio of 76/24 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component.

The primary backings were tufted at 750 rpm on a 1/10 gauge tufting machine with 50 stitches per 10 cm to form a greige carpet weighing 930 g/m².

The stitch holding capacity of a primary backing has been determined by means of tufting a primary backing under conditions which are critical for backtag formation and counting the number of full backtags formed during tufting, i.e., counting the number of tufts which are removed completely from the greige carpet, in an area of 1 m by 12.2 cm containing 9600 tufts. Tufting took place with Groz-Beckert 0660 needles at a gauge of ⅕″ (5.08 mm), Texture Tex PA6.6 tufting yarns type 3252 O 2×1350 dtex, a machine speed of 600 rpm, a speed difference between the supply speed of the primary backing and the output speed of the greige carpet of 6.5%, a stitch rate of 40 stitches per 10 cm and a yarn feed corresponding to a pile length of 11.8 mm. The pile length has been determined by pulling out 100 tufts from the greige carpet and measuring the total length of the removed tufting yarn. The pile length can be calculated dividing the total length of tufting yarn by the number of removed tufts.

The results of example 1 are summarized in Table 1.

TABLE 1 Comparative Properties after tufting Example 1 Example 1 Strength in MD [N/5 cm] 332 336 Strength in CMD [N/5 cm] 236 234 Elongation in MD [%] 56 40 Elongation in CMD [%] 56 49 Stitch holding capacity [—] 19 39

The strength of the greige carpet of example 1 is comparable to the strength of comparative example 1, while the elongation at break is increased, which is especially advantageous for automotive carpet applications. The stitch holding capacity of example 1 has improved as compared to comparative example 1.

Example 2

The primary backing of example 2 was produced by depositing four layers of filaments on a collector surface, each layer of filaments having a weight of 27.5 g/m². The basic weight of the primary backing of example 2 amounted to 110 g/m². The filaments were all of the core/sheath type in a core/sheath ratio of 84/16 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component. The linear density of the filaments was 15 dtex.

The primary backing of comparative Example 2 consisted of four layers of filaments, each having a basic weight of 27.5 g/m². The basic weight of the primary backing of example 2 amounted to 110 g/m². The filaments in layers 1 and 2 were of the core/sheath type in a core/sheath ratio of 77/23 vol. %. The filaments in layer 3 were of the core/sheath type in a core/sheath ratio of 90/10 vol. %. The filaments in layer 4 were of the core/sheath type in a core/sheath ratio of 77/23 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component.

The primary backings were tufted in a shifted manner on a 1/13 gauge Supertufter with 36 stitches per 10 cm to form a greige carpet weighing 476 g/m². The tufted greige was subsequently precoated to lock the tufts into place. The results of example 2 are summarized in Table 2.

The backstitches of example 2 were judged as being smoother and tighter, which is supported by a lower add-on of precoat. Precoating was performed with tenter pins on the precoater.

Mending of example 2 was better than that of comparative example 2. Mendability was tested by pulling a mend in each roll and tested repeated mendability. Example 2 mended as well the third time as it did the first time and had same stitch lock after the third mend as after the first mend.

TABLE 2 Comparative Properties after tufting Example 2 Example 2 Width of tufted section of carpet behind the needles [cm] 188.913 187.960 at the rollup [cm] 187.008 186.690 change in width [cm] −1.905 −1.270 the precoater rollup [cm] 189.865 189.865 total change in width [cm] 0.953 1.905 Width of primary backing behind the needles [cm] 197.644 197.485 at the rollup [cm] 197.326 196.850 change in width [cm] −0.318 −0.635 the precoater rollup [cm] 199.708 200.343 total change in width [cm] 2.064 2.858 Precoat add on [g/m²] 754 795 Tuftbind after precoat [N] 48.2 46.6 Tuftbind in finished Tile [N] 58.5 65.6 Aachen Test width [%] −0.014 −0.010 Aachen Test width [%] −0.006 0.015 Mendability of greige carpet + ∘

Example 3

The primary backings of example 3 were produced by depositing four layers of filaments on a collector surface. For example 3a, each layer of filaments having a weight of 30 g/m². The basic weight of the primary backing of example 3a amounted to 120 g/m². For example 3b, each layer of filaments have a weight of 33.75 g/m². The basic weight of the primary backing of example 3b amounted to 135 g/m². The filaments were all of the core/sheath type in a core/sheath ratio of 84/16 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component. The linear density of the filaments was 15 dtex.

The primary backing of comparative Example 3 consisted of four layers of filaments, each having a basic weight of 33.75 g/m². The basic weight of the primary backing of example 2 amounted to 135 g/m². The filaments in layers 1 and 2 were of the core/sheath type in a core/sheath ratio of 77/23 vol. %. The filaments in layer 3 were of the core/sheath type in a core/sheath ratio of 90/10 vol. %. The filaments in layer 4 were of the core/sheath type in a core/sheath ratio of 77/23 vol. %. The sheath of all filaments consisted of polyamide-6 polymer as the lower melting component. The core of all filaments consisted of polyethylene terephthalate polymer as the higher melting component.

The primary backings were tufted at 900 rpm on a 1/12 (⅛+¼) gauge CMC Scroll tufting machine with 44 stitches per 10 cm to form a greige carpet weighing 645 g/m². The results of example 3 are summarized in Table 3.

TABLE 3 Example Example Comparative Properties after tufting 3a 3b Example 2 Width of tufted section of carpet behind the needles [cm] 187.17 187.96 190.50 at the rollup [cm] 186.69 187.96 190.50 change in width [cm] −0.48 0.00 0.00 Mendability ∘ + ∘

The backstitches of example 3a and 3b were judged as being smoother than comparative example 3.

The mendability of example 3a was judged better than that of comparative example 3, while the mendability of example 3b was judged equal to that of comparative example 3. 

1. A primary carpet backing comprising a nonwoven layer of fibers, wherein the nonwoven layer of fibers comprises fibers comprising two components, a first melting component and a second melting component that melts at a temperature lower than the first melting component, wherein the fibers are 12 to 20 vol. % of the second melting component.
 2. The primary carpet backing according to claim 1 wherein the fibers are 14 to 18 vol. % of the second melting component.
 3. The primary carpet backing according to claim 1 wherein the nonwoven layer of fibers has a uniform composition throughout the nonwoven layer of fibers.
 4. The primary carpet backing according to claim 1 wherein the fibers are bicomponent fibers.
 5. The primary carpet backing according to claim 4 wherein the bicomponent fibers are core/sheath bicomponent fibers.
 6. The primary carpet backing according to claim 5 wherein the bicomponent fibers consist of a polyester core and a polypropylene sheath.
 7. The primary carpet backing according to claim 5 wherein the bicomponent fibers consist of a polyester core and a polyamide sheath.
 8. The primary carpet backing according to claim 4 any of the preceding claims wherein the primary carpet backing is thermally bonded by means of the second melting component of the bicomponent fibers.
 9. The primary carpet backing according to claim 1 wherein the carpet backing comprises additional layers of fibers selected from a nonwoven layer of fibers, a woven layer of fibers or a scrim.
 10. A tufted carpet comprising the primary carpet backing according to claim
 1. 11. The primary carpet backing according to claim 1 wherein the fibers are 15 to 17 vol. % of the second melting component.
 12. The primary carpet backing according to claim 1 wherein the fibers are 16 vol. % of the second melting component.
 13. The primary carpet backing according to claim 1 wherein the fibers have a linear density in the range of 1 to 25 dtex.
 14. The primary carpet backing according to claim 1 wherein the fibers are filaments.
 15. The primary carpet backing according to claim 1 wherein the second melting component has a melting temperature at least 5° C. lower than the melting temperature of the first melting component. 